Effect of rhenium on solidification of Inconel 718 alloy

Abstract

The effect of rhenium (Re) on the solidification of standard Inconel 718 (St-In718) has been investigated by using experimental alloys containing 2·4, 3·5, and 6·0%Re. Rhenium is one of the most powerful refractory elements that improve the high temperature mechanical properties of Ni base superalloys. Results indicate that solidification starts with precipitation of primary γ phase, which is followed by (γ+ NbC) eutectic and (γ+ Ni₂Nb)eutectic. The solidification temperature of the St-In718 is increased by 30 K with the addition of 6%Re. Moreover, the volume fraction of the primary γ is increased, while the volume fraction of eutectic (γ+ NbC) and (γ+ Ni₂Nb) are decreased by the addition of Re. Also, increasing Re content enlarges the secondary dendrite arm spacing (SDAS). Finally, the effects of Re on the partition coefficients k of alloying elements to primary γ and to eutectic γ+ NbC were evaluated and Re was found to segregate preferentially to the primary γ.